The present invention relates to a cylinder head cover for a cylinder head of an internal combustion engine.
Known cylinder head covers are placed on the cylinder head of an internal combustion engine and are secured to the cylinder head by attachment bolts. The attachment bolts are usually guided through attachment lugs formed on the cylinder head cover and are screwed together with the underlying cylinder head to secure the cover. To obtain a fluid-tight seal, a circumferential gasket is inserted into the contact region between the cylinder head cover and the cylinder head. This gasket runs through the region of the attachment lugs on the cylinder head cover and is pressed in the attachment direction by the attachment bolts. The tightness between the cylinder head cover and the cylinder head in this prior art solution is ensured by pressing the sealing element in the direction of the attachment force generated by the bolts. The effective direction of the sealing force transmitted by the sealing element matches the effective direction of the attaching force produced by the attachment bolts.
Because the sealing element is pressed in the direction of the attachment force, the resulting restoring forces are high and are transferred from the compressed sealing element to the cylinder head cover and can, particularly at elevated temperatures, lead to a relaxation of the cylinder head cover, which is typically formed of synthetic resin material (i.e., plastic). To prevent such a relaxation, which could lead to leakage, the pressing force of the cylinder head cover on the cylinder head must be reduced. This involves the risk, however, that seal tightness will also decrease.
Increasing the number of attachment bolts can reduce this relaxation since this achieves an approximately uniform surface pressure. The rigidity of the cylinder head cover can furthermore be improved with additional ribs. Both of these measures, however, add weight to the cylinder head cover and are associated with additional costs.
Also to be taken into account is the fact that because of the different linear expansion coefficients of the cylinder head cover, which is formed of synthetic resin material, and the cylinder head, which is usually made of aluminum, the gasket is also subject to pushing and shearing forces, which further stress the gasket.